Acoustic device.



M. C. HOPKINS.

Acousnc DEVICE.

APPLICATION FILED APK. l?, |918.

Romae which reproduce sounds; and is particularly directed to the attainmentof a direct prepa;A

UNITED STATES "Ina'ifliNTV oEEIeE.

MARCUS C.'HOPKINS, 0F NEW YORK,

LEKTOPHONE CORPORATION, OF

N. Y., nssIGNon, BY nEsN-E ASSIGNMENTS, To NEW-'roam N. v., a conPonA'rIoN or DELAWARE.

ac oUsTIc DEVICE. j

Spccmcation of Letters Patent:

original application mea .my 14, 1913. serial .No- 173226. Renewed nai-eh 22, 191s, serial 110.224,0'48.

Patented July 2, 191e.A

Divided and this application led April 17, 19l8f Serial No. 229,014.

To all whom t 'may concern:

Be it known that I, MARCUS C. HOPKINS,

a citizen of the United States, residing in Y the borough of Manhattan, city, county, and

State of New York, have invented certain new and useful Improvements in Acoustic Devices; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the vart to make and use the same.

This invention relates to instruments ation, in free air, from a record or equiva- -ent element subjected to the action of the originalso'und Waves or vibrations, of selfsnstaming sound waves substantially corre- Y sponding inlintensityand. amplitude, as well .2a.

as inpitch or. timbre, to the said original sound waves, as distinguished from an initial generation of violent.. air disturbances in a confined space, and a subsequent transformation of such disturbances into self? sustaining sound waves by means of a megaphone, horn or other amplifier. Y

In the lcase of a talking machine,'the de- A vice employed. to 'propagate theregenerated sound waves in arcomprises the reproducer or `,soun'dj-.hvoxand the horn; but the reproducer alone is incapable of propagating;

sound waves of the "character above stated because of the fact that the air disturbances which 'are heat and tocontrol the-lateral form of the' Wave during a progressive spreading action produced by its diaphragm and which issue through its mouth-piece are al. most immediately dissipatedin heat or in waves -which are not heard at any considerable distance if the horn be removed. Conl. "scquently,'it'is usual in .all instruments of v sof the4 class indicated to employ an amplifier of some sort to resist transformation into which is accompanied by 'a lessening of the violence of -the disturbance until a wave front of lgreat area is attained havinga movement appropriate to the sound conductivity of air. In this way, it has been found ord, into A Y but in every 'instancesuch method has been practicable to transform a of theA ener?,

satisfactory part sustaining sound waves in air;

accompanied by distortions of the true recorded sounds in the reproducer, more which it appertains to obtained `from a T moving recparticularly in the horn 'or amplifier, givand overtones, the loss of timbre in instrumentsand the voice, and the accentuation of notes of certainpitch, so change the recorded number that a `faithful reproduction is not obtained.

Itis the object of the present invention to regenerate the original sounds directly from the record or other element subjected to the action of such sounds, without interposition of'a confined bodyof air and with- Aoutthe employment vof a restrictive trans-y former,'snch as` a horn. According to the invention, the sound regenerator comprises a. tympanum ofrelatively great area freely exposed Ato unconfined air, 1n which the sounds are to be propagated.; the vibrations" produced by the record or its uivalent,-v that is, the element on- Which t e original sounds or sound waves,v are 'recorded, or which is otherwise subjected to ing action of said sounds or, sound; Waves and ma 'thei'efoie, Abetermed the soundvibrate clementebeing .faithfully trans- Vmitted to the rtylnpanum in such manner thattlxe latter excites directly in the free air surrounding it, sound waves of an intensity and vamplitude"substantially corresponding to theoriginal sound Waves; In other words Ythe original sounds are directly regenerated by the vibrating tympanum without theinterposition of a restrictive or sound-modifying transformer.

the vibrat- The invention consists, briefly, inthe provision of a' tympanum of novel construction, which is capable of responding to the high frequency vlbrations employedin the re roduction of sounds, and of imparting t ese vibrations to a large body of air; and .it 1s to beconsidered as a divlsion .of the invention-shown and described in my rior application, renewed March 22, 1918, o. 224,048.

The accompanying-drawing illustrates the improved tympanum incorporated' 1n a sound-reproducing machine of the kind disclosed said application, the single figure being a vertical sectional view taken transversely through the machine. Reference rugations as just suggested, some variation from the Vproportions above given may be made; but such variations will not be great. The tympanum should preferably be constructed of a colloidal substance, and should be from 3 to 20 thousandths of an inch in thickness ,according to the crispnes's or stiff character of the material used. Compressed fibrous material, such as hot. pressed paper or fiber, has been found to act satisfactorily.

It will be` noted that in the construction illustrated, the arms of the spider J incline downwardly to correspond with the conical shape of the tympanum L, the apex of the conical portion of the tympanum pointing upwardly toward the deck A of the cabinet, and, also, that the'concave side of the said tympanum is open to the surroundin atmosphere through the o en bottom o? the cabinet, no obstructions ing presented to the sound 'waves issuing from the concave surface of the tympanum. 4

A cap M is secured to the 'apex of the conical portion Z of the tympanum, and this cap should be of more rigid construction. than the remainder of the tympanum'and should preferably be three-eighths of an inch or more in diameter. I prefer to make the cap M of metal, extremely light -but very rigid, and in the form of two cones m, m screwed tightly together upon opposite sides of the t`I panum so as to grip the material thereofwith their edges. In order that a tight and, positive application of the cones forming the cap to the conical portion of the tympanum may be had, it is preferable to form the inner cone m' of lesser angle, and the outer cone fm, of greater angle than the said conical portion, in which case their edges will securely grip the tympanum material when they are fastened together.

The vibrations or sound waves originally imparted to the record or its equivalent may be transmitted therefrom to the tympanum to vibrate the same in the manner and by means of the mechanism shown and described in my aforesaid application above identified, or by means of some other approved transmission means or mechanism, as will be understood. In. any event, such means or mechanism for'ns no part ofA the present case, however, and for that`reason requires no extended disclosure. It is believed suiiicient to state, therefore, that in the arrangement illustrated the mechanism in question is located Within-the horizontal arm g of the support G, and is connected at its forward end with the stylus holder g, the other end of said mechanism having connected to it a vertical rod V, whichgextends downwardly through the interior of the vertical arm g -of the support and is rigidly secured to the cap M of the tympanum. In consequence, the vibrations of t e stylus g mounted in said holder and produced in the usual wayv by the phonic lines on the` record, will be transmitted from the stylus through the transmission mechanism to thel rod V, which will be vibrated endwise, the endwise vibrations of said rod being directly impressed upon the tympanum L.

I claim:

1. An acoustic device, comprising a tympanum rigidly supported at its periphery and having a free area exceeding nine lnches in diameter and a conical portion, the diameter of whichis notless than eight-tenths of the diameter of said free area.

2. An acoustic device, comprising `a tympanum rigidly supported at its periphery and having a free area exceeding nine inches in diameter and a conical portion, the diameter of which is not less than eight-tenths of the diameter of said free area, said conical portion being rigid in the direction of the axis v of the tympanum.

3. An acoustic device, comprising a tympanum rigidly supported at its periphery and having a free area exceeding nine inches in diameter and a conical portion, the diameter of which is not less than eight-tenths of thediameter of said free area, the altitude of said conical portion being substantially onequarter of the diameter of its base.

4. An acoustic device, comprisingatympanum support having a circular aperture, and a light tympanum freely'exposed to unconfined -air and having its outer edge rigidly mounted on said support in said aperture; said tympanum having a central conical portion, the base of which exceeds in area onehalf the effective area of the said tympanum the tympanum being of suilicient area to im part to the surrounding free air, when vibrated, sound waves substantially corresponding in intensity to the original sound waves.

5. An acoustic device, comprisingatympanum support having a circular aperture, and a light vibratileA tympanum exceeding nine inches in diameter, having its outer edge rigidly mounted on said support; said tympanum being shaped to provide an annular rim adjacent said support, and a conical Vportion `springing from the inner edge of said annular rim, the diameter of the base of said conical portion being not less than eight-tenths of the said circular aperture in sa1d support.

6. An acoustic device, comprisingatympanum support having a circular aperture, and a light vibratile tympanuminounted in said aperture and having its outer edge secured to said support; said' tympanum being shaped to provide an annular rim, the outer diameter' ofwhieeexeeeds nine inches, :md

' e conieei gortioii springing from the inner i edge ofiseid; emular-rim, the eitimde of sei@ onieeletion being subetensieiy one fourth o the diameter ef its bese.

7., Au .acoustic device, comprising e. tympe num suppol; having e circuler aperure' exceedm nine inches in diameter, en@ e lighe vlbret e tympemzm mounted in seid eper- ,ture 'and having its outer edge rigidly secured to seid suppoit; seid. tym'penum'bemg `.the diameter of the base of said eonieelportion being not lessuthan eight-tenths of the eeem'ee diemetei:3 of seid circuler aperture, end the aiitudle sei@- eoiiieefi periexi being subtantieiiy eee-geweer of the diameter of its f eee 8., Afm eeoustie eviee,wmprising a tympamim emmying e bodily movable, central .cenieperieii, and en Amamie? rim which eneircies seid conical portion m which is rigiliy supported, sei camice-i porion being freely exposed en eil sides @o uncoiiined si? and being o suiieient ereg, to produce self-sustaining soun waves in the surrounding air when vibrate, substentieiiy es described.

n testimony whereof ex my signature.

MARCUS C. HOPKNS. 

